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Quik Stop Station No.07 N4I' February 8, 1999 Stockton California Tank Closure Repo noticeable holes and only minor rusting and pitting. The USTs were transported for disposal to the West Coast Equipment facility in Turlock, California. The excavated sandy backfill materials from above and around the former USTs were transported to and stockpiled at the Forward Landfill (Forward) facility prior to disposal or recycling by Forward. Subsequent to the removal of the two USTs, soil samples were collected from depths between approximately 14 feet to 16 feet below surface grade (bsg) from the north ends of each former UST (T-1-N-14'/2 and T-2-N-15'/2) and from the south ends (fill and turbine ports are both at the south end) of each former UST (T-1-S-14, T-1-S-16, and T-2-S-14). The sampling locations are shown on the Site Plan (Figure 2). The subsurface soil encountered beneath the site consisted of clayey silt.. No soil samples were collected from beneath the product lines or the dispenser island, as these structures and the underlying soil were completely excavated and removed to a depth of approximately 12 feet during the excavation work for removal of the two USTs. Ms. Letitia Briggs of the SJCPHS/EHD was onsite to observe the soil sampling locations and sampling activities. Analvtical Methods and Results All of the soil samples were prepared, chilled and transported under chain-of-custody (COC) protocol to Kiff Analytical (Kiff), a State-certified laboratory in Davis, California (Certification No. 2236). The requested analyses included: total petroleum hydrocarbons as gasoline (TPHg), the gasoline constituents benzene, toluene, ethylbenzene, and total xylenes (BTEX), and the five oxygenated fuel additive compounds methyl tertiary-butyl ether (MTBE), di-isopropyl ether (DIPS), ethyl tertiary butyl ether (ETBE), tertiary amyl methyl ether (TAME), and tertiary butanol (TBA) by modified Environmental Protection Agency (EPA) Method 8260B, and Total Lead on the T-2 samples by EPA Method 6010. The laboratory results are summarized in Table 1. Copies of the laboratory and COC reports are included in Attachment C. Summary Former USTs Excavation Analytical results of soil samples collected from beneath the two former USTs indicated the following: • TPHg and BTEX: There were no detectable concentrations of TPHg, and only low concentrations of BTEX were detected in the native soils beneath the southern end of UST T-1 at depths of approximately 14 feet (0.0052 ppm ethylbenzene and 0.056 ppm xylenes) and 16 feet(0.051 xylenes). • MTBE: Low concentrations of the fuel oxygenate MTBE were detected in the native soils beneath the south end of former UST T-1 at depths of approximately 14 feet (0.0073 ppm) and 16 feet (0.094 ppm). No detectable concentrations of the fuel oxygenates DIPS, ETBE, TAME, and TBA were present in any of the soil samples. 7076-1 l.tcr 2 HORIZON ENVIRONMENTAL INC.